Electrical reproducing device



April 1, 1930.

l ELECTRICAL REPRODUCING DEVICE Fliled Dec. 22, 1924 2 Sheets-Sheet l Tflg. 1'

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"Im:| all" Z0 7 INVENTOR F. 1 DYER 1,752,943

ELECTRICAL REPRODUCING DEVICE Filed Deo. 22, 1924 2 sheets-Sheet 2' Patented Apr. l., 1930 FRANK L. DYER, F IONTGLIB, NEVI murieron. nnrnonucrne Dnvrcn application mea December se, im. sei-m1 no. maas.

, My present invention vrelatesto an im.-v

proved device for securing .electrical reproduction from a talking machine record, and particularly from a talking machine record 5 whose record groove is of microscopic size as set forth in my Patent No. 1,570,297, issued Jan. 19, 1926. In securing electrical reproductionofrom a talking machine record the needle engaging the record roove results in 10. the production of minute te ephone currents correspondingl to the record, and which may be heard either directly in an ordinary telephone receiver, or be reproduced after suitable amplification by means of a device' of the type of a radio loud speaker. When a record groove is of microscopic size as disclosed inv said ap lication, with the amplitude of the recorde waves proportionally reduced, it is not possible to secure satisfactory reproduction b direct means such as a diaphragm and horn, ecause the record is too faint. Therefore some mechanism outside and independent of the record is employed to ive the necessary amplification, and the mo ern vacuum tubes provide ideal means for this 4purpose since any reasonable degree of amphfication can be secured by them with very little distortion. With such a microscopic groove it is important that the needle shall track the groove with very little pressure in order to prevent undue wear, both of nthe record surfacel and the'needle itself, and even if resent forms of devices are emplo ed, the lig tness of pressure can be secured counteracting springs or by suitably balancmg the reproducing elements. However I have foundinexperixnentwith extremely microscopic record grooves that it is diicult to have the grooves always in accurate relation to the center of the record, and as a result the needle partakesv of a 4alight movement sidewise back and forth in playing the record. This diiculty'may be. due to de e cts in the recording machines or to defects'which arise in the process of duplication, or to lost motion' between the record and the centering pin on the reproducing machiie. Whatever the cause maybe, the fact is that I have observed an inevitable tendency of the needle to move from side to side during the playing of the record. With an orfects referred to.

dinary standard record groove of the order of .005 inch in width, and with a relatively heavy needle yengaging such a groove and quickly wearing to entirely lill the same, this movement from side to side is not serious even though the sound box and the parts associated therewith are relatively heavy. But

with a very microscopic groove I ndthat the movement from side to side causes the needle to shoulder very rapidly, and in some cases the needle does not follow the groove throughout its length. It therefore becomes necessary to reduce the inertia of the device as much as possible so as to reduce the detrimental effects due to the movement of the needle from side to side, and to this endpI have constructed an -improved electrical reproducing device in which the heavier parts are located close to the pivot, permitting the needle to swing Aacross the record in transversing the record groove. In 'my improved construction the needle and the supports therefore are located at the end of a very light tube, having little inertia so as to minimize-the detrimental ef- Preferably I generate the telephone currents which are to be ampliied, by a magnetic or inductive device, rather than by micro-t phone contacts, as in this way the telephone currents will be more free of distortion, and 30 at the same tlme the telephone construction permits simplier and more effective connection to be made with the needle arm.

In orderl that my invention may be better understood attention is directed to the accompanying drawings forming part of this specification, and inwhich:

-Fi 1 is an elevation partly in section showing a turn table carrying a record thereon, and with my improved reproducing device in connection therewith Fig. 2 is a section on an enlarged scale ofa pivot, and the parts comprising the telephone transmitter showingan arrangement in which the telephone currents are generated 05 by the vibration of a coil in a magnetic vfield: A Fig. 3 a sectionalview at-right angles Vto Fig. 4 asectional view on the line 4--4 of Fig.2: r

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Fig. is a side view partly in section on an enlarged scale of the forward end of the supporting tube, the needle arm and the needle:

Fig. 6 a similar view at right angles to Fig. 7 a front view of'Fig. 5:

Fi 8 a detail sectional view showing a modi ed form of telephone transmitter: and

Fig.- 9 a corresponding view at right angles to Fig. 8.

In all the above views corresponding parts are represented by the same letters of refer,

ence.

In Fi 1 a turn table 1 is shown carrying a recor 2 with which cooperates a needle 3 at the end of a light tube 4 made preferably of aluminum. This tube 4 is secured to a casing 5 which is mounted between pivots 6.-6 so as to permit the needle 3 to be moved up and down to accommodate any mechanical variations in the record. This also rmits the needle to be changed when desir The ivots` 6 are carried in the ends of a yoke 7 Vliving a stem 8 fitting in the socket 9 and bearing preferably on the b'all or ivot 10 whereby the arm 4 maybe swung ack an forth across the record during, the laying of thesame. The casing 5 is provi ed with a complementary part 11 secured to the same.A SCleWS 28-28 @D by screws 12 and formed with an integral box 13 in which is located a permanent magnet 14 (Figs. 2 and 3) having preferably a central core or leg 15. A very light tube 16 works over the core 15 and between the le piecesof the magnet and carries a coilm17 in which the telephone currents are generated. These parts in Fig. 3 are somewhat exaggerated. The supporting cylinderA 16 in practice should be made extremely thin referably of bakelite or similar material an the turns of the coil 17 should be very close t0- gether. The support -16 is carried by a light arm 18 secured to a resilient strip 19' made preferably of highly tensioned spring steel. This strip 19 is provided at its ends with integral blocks 20, having conical holes therein with which the tapered ends of adjusting screws 21-21. engage. By means of these screws the spring 19 may be placed under the desired tension, and at the same time the position of the-stri rately osition the coilA 17 with respect to the po es of the magnet 14. Thus it will be seen that if the lower screw 21 is slightly 'withdrawn and the corresponding upper screw issli htly advanced the 19 will imag sp g jp ver slightly in an upward direclon, 1g. 3. y 'reversing the operation of these screws the sprin will be adjusted in the. othe'r direction onnecting with the sprinrw isa very light hollow rod 22 leading t ou h the tube 4 to the needle arm 23, shown in igs. 5, 6 and 7./ This needle arm 23 1 s mountje between v'ertical pivots'24 and is right angular in-form, its longitudinal leg may be adjusted to accubeing provided with a suitable recess to receive t e needle 3 which is held in place by, a clamping screw 25. The lateral leg of the needle arm is secured to the flattened outer end of the tubular rod 22 by means of a l screw 25'l as shown in Fig. 6. It will be seen A that the spring 19 retains the needle arm and needle in their normal position but at the same time when the .needle vibrates, the spring 19 will act like an aperiodic dia phragm and will permit the coil 17 to vibrate in the magnetic field to thereby generate extremely minute telephone currents which are suitably amplified by means of properly arranged vacuum tubes which lead to a suitable radio loud speaker. If the currents are of suiiicient magnitude as not to require amplifcation they may be heard directly in a telephone receiver. In Figs. 8 and 9 a modified form of telephone transmitter is shown in which a magnet 26 is rovided with two coils 27 27 working adjacent to the spring 19. With this arrangement the Vibration of the spring 19 yvill generate the currents in the coils 27 which are ,then suitably amplilied. In order to provide for -very accurate adjustment of the magnet 26 with respect to the spring 19 I employ two 'adjusting aging conical holes in the magnet as shown 1n Fig'. 8. By loosening upper screw 28 in this ligure Vand tightening the lower screw the magnet 26 willmove to the right where y reversing the adjustments of these screws it will be moved to the left. It will be understood, that instead of generating the tele hone currents nductively, the vibrations o the spring 19 may be made use of to vary the contact between microphone electrodes, in the well known way. 1t will be seen that the device .is one in which most of the mass is located close to the pivot 8 so that inertia is very much reduced, at the same time a very flat construction is presented permittin -a relatively shallow cover 29, see ig. 1, to e used, thus making'it possible to house the entire apparatus in a cabinet of small size. l

Having now described my invention, what I claim as new therein and desire to secure by Letters Patent is as follows:

1. In an electrical reproducing device the combination of an arm, a needle arm pivoted to the same at one end, a substantially aperiodic flat spring mounted at the other end of the arm, said spring being adapted to maintain the parts in normal position, connections for transmitting vibrations reciprocal ly between theneedle arm and said spring and telephone transmitter mechanism o erated by theA vibration of the needle arm, su stantially as set forth.

2. In anelectrical reproducing device the combination of a magnet, a coil iniuenced by the field of said magnet, a substantially aperiodic fiat spring supporting said coil, means for-tensioning said .V-prin a. needle arm and connections to trans :uit vi 1y between said needle arm'and said spring, substantially asset orth. y

3. In ai; electrical reproducing device the combination of a substantially aperiodic Hat spring, Intens at both ends of the spring for tensioning the same, a needle arm, connec tions for transmitting the Vibrations reciprocally between said needle,- arm and said spring and a telephone transmitting device actuated by the vibrations of said needle arm, substantially as set forth.

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4. In an electrical reproducing device the combination of a flat spring, means at bothV ends of the spring for tensioning the same and for simultaneously adjusting the spring bodily, a needle arm, connections for transmitting vibrations reciprocally between the needle arm and said spring and telephone transmitting mechanism actuated by the vibrations of said needle arm, substantially as set forth.l

l This specification signed and witnessed this 17th day of December, 1924.

FRANK L. DYER.

rations reciprocal- K 

